Currently, large generators and motors, and fundamentally, permanent magnet synchronous machines are cooled by water in a way that heat generated by the stator coil winding heads and by other copper and metal, etc. can be extracted from the air inside.
Decreasing the temperature of the air inside is essential for these enclosed machines, as their rotors have magnets with which the voltage and power developed by the machine are generated.
FIG. 1 shows one of the cooling systems which is currently most often used in an enclosed machine, which is the system known as “water jacket” 11, which, with the use of a series of grooves 13 made on the outer surface of the jacket, provides the circulation routes or channels for the refrigeration liquid, normally water. The “water jacket” 11 is fastened to the machine's outer housing 15 to complete the water circuit. Generally, the stator pack 17 with its coils 19 are placed inside the jacket 11 so that the source of the heat generation, which is the copper, is as close to the water as possible, in order to produce a thermal exchange by conduction, or by convection if there is any element capable of moving the internal air, or by radiation. FIG. 2 shows a “jacket” 11 with its channels 13 helicoidally arranged for water circulation.
Depending on the application, and fundamentally on the quality and properties of the refrigeration liquid which circulates through the “jacket”, the jacket may or may not need to be made from stainless steel in order to prevent the corrosion of its internal channels as a result of the refrigerant liquid circulation.
Among the disadvantages of the refrigeration system just described, the following are worthy of mention:                The need for said “jacket” to be made from stainless steel to prevent corrosion.        The high cost of machining the “jacket” in order to create the aforementioned channels.        The need for a closing element for the “jacket”, which will act as the machine housing, in order to complete the refrigeration circuit.        
This invention intends to resolve these issues.